Machinery's Handbook, 31st Edition
CNC FIXED CYCLE CODES 1369 The cycle will start feeding from the R-level to the Z-depth, where the tap stops, reverses its rotation and feeds back to the R-level, where it stops again and resumes normal spindle rotation (see Fig. 19). G84 cycle must be programmed with spindle rotation CW (normal), typical in M03 mode.
G98
G98
G99
G99
Spindle CCW - M04
Spindle CW - M03
Z0
Z0
Z-depth
Spindle CW - M03 Z-depth
Spindle CCW - M04
Fig. 19. G84 Fixed Cycle. Fig. 20. G74 Fixed Cycle. Left Hand Thread (G74): The G74 fixed cycle is used for cutting a left hand thread and has the following format N__ G99 (G98) G74 X__ Y__ R__ Z__ F__ G74 cycle must be programmed with spindle rotation CCW (reverse), typical in M04 mode. In all other respects, G74 is identical to G84 (see Fig. 20). Boring Cycle (G85): The G85 fixed cycle is used for boring and has the following format N__ G99 (G98) G85 X__ Y__ R__ Z__ F__ From the R-level, the boring bar will feed to the Z-depth, than feeds back to R-level, both at the programmed feed rate F__. A similar cycle G89 has a dwell at the bottom of the hole. Either one of these cycles is commonly used for reaming (see Fig. 21).
G98
G98
G99
G99
Z0
Z0
Z-depth Spindle stop
Z-depth
Fig. 21. G85 Fixed Cycle. Fig. 22. G86 Fixed Cycle. Boring Cycle (G86): The G86 fixed cycle is used for boring and has the following format: N__ G99 (G98) G86 X__ Y__ R__ Z__ F__ In G86 mode, the boring bar will feed from the R-level to the Z-depth, where the spindle stops rotating and the tool is retracted at a rapid rate. Note that a straight line (tool mark) will be generated on the bored hole (see Fig. 22). Boring Cycle (G76): The G76 fixed cycle is used for fine boring and has the following format: N__ G99 (G98) G76 X__ Y__ R__ Z__ Q__ F__ This cycle is called a “ fine ” boring cycle, because it does not leave any tool marks on the bored hole. The Q__ in the block is the amount of shift away from the hole centerline that
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online